1. Field of the Invention
The present invention relates to a method and a system for controlling idle revolution number of an engine depending on a state of a driving load of an automatic transmission.
2. Description of the Prior Art
As to a conventional system for controlling engine revolution number, an idle revolution number control in due consideration of effects of state of load of an automatic transmission exerted on the engine driving condition is being carried out, as disclosed in the Japanese Publication Patent No. H02-057211, by setting an idle target revolution number using informations such that whether the shift position of the automatic transmission is in nonrunning range or in running range upon carrying out detection of position of shift lever of the automatic transmission.
Now, the hydraulic automatic transmission carries out the speed change control by controlling the oil pressure within the automatic transmission, and then, if delivery power of an oil pump happens to change due to change of engine revolution number and oil temperature and the like, time required for speed change too changes. In the case where the delivery power of the oil pump is lowered that is seen, for example, when the engine revolution number is low due to an extremely high temperature or an extremely low temperature, the time required for speed change operation becomes long and therefore, there was a problem to produce a time delay until completion of actual speed change from the time when the shift position of the automatic transmission is changed.
This is to say that because, in the conventional idle revolution number control system, judgement of whether the driving load exists or not is made based on whether the shift lever position is in running range or nonrunning range, that system can not cope with the time discrepancy between the timing of shift lever position change from being changed to the nonrunning range to the running range and that of actual clutch cloupling of the automatic transmission, and thus there was a case where a spouting up of the engine revolution number was induced.
As a measure against this situation, for example according to Japanese Laid-Open Patent Application No. H05-280400, an arrangement is made such that the idle target revolution number is changed with a delay by a predetermined time, which is decided depending on oil temperature of an automatic transmission, from the time when the shift position is changed from nonrunning range to running range.
However, even if an arrangement is made such that the idle revolution number is maintained to the target idle revolution number of nonrunning range within a predetermined time, which is decided depending on the oil temperature of the automatic transmission, from the time when the shift position is changed from the nonrunning range to the running range as disclosed by the prior art as given above, due to the fact that the control factor is the oil temperature only, there was a problem such that any countermeasure could not be devised when delivery power changes were to be caused by factors other than the oil temperature.
The present invention has been made to solve the foregoing problems and provides method and system of an idle revolution number control system being capable of preventing a spouting up of engine revolution number caused by unmatched condition between the shift position change of the automatic transmission and the change of actual condition of driving load.